1. Field of Invention
The present invention relates to display of seismic data, such as seismic reflection strength, for locating hydrocarbon deposits.
2. Description of Prior Art
Factors affecting the strength of seismic reflections are set out by O'Doherty and Anstey in the paper "Reflections of Amplitudes," Geophysical Prospecting, Volume XIX, No. 3, page 430.
It is known that variations of seismic reflection strength along a profile or over a survey may be due to several causes; among others, they are sometimes associated with focusing effects, sometimes with interference effects, sometimes with highly absorptive regions above the reflector, and sometimes with change in the physical properties of the material above or below the reflecting interface. One circumstance which is of interest in connection with the last of these causes is that of hydrocarbon saturation, which can produce significant changes in the physical properties of a reservoir rock. Such changes produce variations in reflection strength if they include changes in the seismic velocity and/or density of the rock.
In the direct location of hydrocarbons by the seismic method, therefore, it becomes important to establish whether observed changes of reflection strength are due to changes of velocity and/or density, or to other effects.